Loop quantum cosmology from quantum reduced loop gravity

¹ Instytut Fizyki Teoretycznej, Uniwersytet Warszawski - ul. Pasteura 5, 02-093 Warszawa, Poland, EU
² Institute for Theoretical Physics, University of Wrocław - Pl. Maksa Borna 9, PL-50-204 Wrocław, Poland, EU

Received: 13 March 2015
Accepted: 3 August 2015

Abstract

We show how loop quantum cosmology can be derived as an effective semiclassical description of loop quantum gravity. Using the tools of QRLG, a gauge fixed version of LQG, we take the coherent states of the fundamental microscopic theory suitable to describe a Bianchi I Universe and we find a mapping between the expectation value of the Hamiltonian and the dynamics of LQC. Our results are in agreement with a lattice refinement framework for LQC, thus the so-called “old” and “improved-dynamics” regularization schemes can be reproduced. These amount to different choices of relations between local variables and the smeared ones entering the definition of the coherent states. The leading order of the fundamental theory corresponds to LQC, but we also find different inverse volume corrections, that depend on a purely quantum observable, namely the number of nodes of the states.